Summer circumpolar acoustic occurrence and call rates of Ross, Ommatophoca rossii, and leopard, Hydrurga leptonyx, seals in the Southern Ocean

Abstract Two of the Antarctic pack ice seals, Ross, Ommatophoca rossii , and leopard, Hydrurga leptonyx, are extremely difficult to study via traditional visual survey techniques, yet ideal for an acoustic as they highly vociferous produce array underwater sounds during austral summer. To determine their occurrence in ice, we use calls, detected within 680 recordings made between 1999 2009 part two multinational programmes. Siren calls Ross seals were mainly January, 9.88 per minute from low siren was highest call rate this species. High numbers seal close edge areas 0° 20° E 60° 130° E, suggesting these important summer habitats. Leopard December had percentage calls. Call 11.93 double trills leopard seals. throughout Southern Ocean with more ice. There little spatio-temporal overlap but both species vocally active day. Longitude latitude most predictors occurrence, month year predicted occurrence. This is first examine circumpolar